From: Eric Biggers ebiggers@google.com
commit f699594d436960160f6d5ba84ed4a222f20d11cd upstream.
GCM instances can be created by either the "gcm" template, which only allows choosing the block cipher, e.g. "gcm(aes)"; or by "gcm_base", which allows choosing the ctr and ghash implementations, e.g. "gcm_base(ctr(aes-generic),ghash-generic)".
However, a "gcm_base" instance prevents a "gcm" instance from being registered using the same implementations. Nor will the instance be found by lookups of "gcm". This can be used as a denial of service. Moreover, "gcm_base" instances are never tested by the crypto self-tests, even if there are compatible "gcm" tests.
The root cause of these problems is that instances of the two templates use different cra_names. Therefore, fix these problems by making "gcm_base" instances set the same cra_name as "gcm" instances, e.g. "gcm(aes)" instead of "gcm_base(ctr(aes-generic),ghash-generic)".
This requires extracting the block cipher name from the name of the ctr algorithm. It also requires starting to verify that the algorithms are really ctr and ghash, not something else entirely. But it would be bizarre if anyone were actually using non-gcm-compatible algorithms with gcm_base, so this shouldn't break anyone in practice.
Fixes: d00aa19b507b ("[CRYPTO] gcm: Allow block cipher parameter") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- crypto/gcm.c | 34 +++++++++++----------------------- 1 file changed, 11 insertions(+), 23 deletions(-)
--- a/crypto/gcm.c +++ b/crypto/gcm.c @@ -597,7 +597,6 @@ static void crypto_gcm_free(struct aead_
static int crypto_gcm_create_common(struct crypto_template *tmpl, struct rtattr **tb, - const char *full_name, const char *ctr_name, const char *ghash_name) { @@ -638,7 +637,8 @@ static int crypto_gcm_create_common(stru goto err_free_inst;
err = -EINVAL; - if (ghash->digestsize != 16) + if (strcmp(ghash->base.cra_name, "ghash") != 0 || + ghash->digestsize != 16) goto err_drop_ghash;
crypto_set_skcipher_spawn(&ctx->ctr, aead_crypto_instance(inst)); @@ -650,24 +650,24 @@ static int crypto_gcm_create_common(stru
ctr = crypto_spawn_skcipher_alg(&ctx->ctr);
- /* We only support 16-byte blocks. */ + /* The skcipher algorithm must be CTR mode, using 16-byte blocks. */ err = -EINVAL; - if (crypto_skcipher_alg_ivsize(ctr) != 16) + if (strncmp(ctr->base.cra_name, "ctr(", 4) != 0 || + crypto_skcipher_alg_ivsize(ctr) != 16 || + ctr->base.cra_blocksize != 1) goto out_put_ctr;
- /* Not a stream cipher? */ - if (ctr->base.cra_blocksize != 1) + err = -ENAMETOOLONG; + if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, + "gcm(%s", ctr->base.cra_name + 4) >= CRYPTO_MAX_ALG_NAME) goto out_put_ctr;
- err = -ENAMETOOLONG; if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME, "gcm_base(%s,%s)", ctr->base.cra_driver_name, ghash_alg->cra_driver_name) >= CRYPTO_MAX_ALG_NAME) goto out_put_ctr;
- memcpy(inst->alg.base.cra_name, full_name, CRYPTO_MAX_ALG_NAME); - inst->alg.base.cra_flags = (ghash->base.cra_flags | ctr->base.cra_flags) & CRYPTO_ALG_ASYNC; inst->alg.base.cra_priority = (ghash->base.cra_priority + @@ -709,7 +709,6 @@ static int crypto_gcm_create(struct cryp { const char *cipher_name; char ctr_name[CRYPTO_MAX_ALG_NAME]; - char full_name[CRYPTO_MAX_ALG_NAME];
cipher_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(cipher_name)) @@ -719,12 +718,7 @@ static int crypto_gcm_create(struct cryp CRYPTO_MAX_ALG_NAME) return -ENAMETOOLONG;
- if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "gcm(%s)", cipher_name) >= - CRYPTO_MAX_ALG_NAME) - return -ENAMETOOLONG; - - return crypto_gcm_create_common(tmpl, tb, full_name, - ctr_name, "ghash"); + return crypto_gcm_create_common(tmpl, tb, ctr_name, "ghash"); }
static struct crypto_template crypto_gcm_tmpl = { @@ -738,7 +732,6 @@ static int crypto_gcm_base_create(struct { const char *ctr_name; const char *ghash_name; - char full_name[CRYPTO_MAX_ALG_NAME];
ctr_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(ctr_name)) @@ -748,12 +741,7 @@ static int crypto_gcm_base_create(struct if (IS_ERR(ghash_name)) return PTR_ERR(ghash_name);
- if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "gcm_base(%s,%s)", - ctr_name, ghash_name) >= CRYPTO_MAX_ALG_NAME) - return -ENAMETOOLONG; - - return crypto_gcm_create_common(tmpl, tb, full_name, - ctr_name, ghash_name); + return crypto_gcm_create_common(tmpl, tb, ctr_name, ghash_name); }
static struct crypto_template crypto_gcm_base_tmpl = {